At Los Alamos during the Manhattan Project -- Project Y, as it was called -- badges served multiple purposes. They said who was allowed inside the facility, sure. No badge, no entry. But they were also color-coded to describe the breadth of your access. Yellow meant that you could go into technical areas of the lab, but could receive no classified information -- like guards. Blue was for people who needed classified information but not technical information -- clerks and warehouse employees. Red was for people who could get some technical information within a highly compartmentalized state -- technicians and secretaries. White was for those who could know it all -- everything that was to be done at Los Alamos. Early on, General Groves had wanted Los Alamos to be considerably compartmentalized, but Oppenheimer and others fought it. The result was that white badgers had the run of the lab, more or less, and could attend laboratory-wide colloquia.